Mork first met Exidor in Episode 4 "Mork Runs Away". Mork moved out of Mindy's apartment so she could date human males. He moved into a flop house. He noticed a sign on a door claiming the dwelling belonged to the "Friends of Venus". Mork popped in, hoping to meet some Venusians he used to know on Venus. Instead he met Exidor.

Exidor was a crazed leader of a UFO cult called the Friends of Venus. One of the problems with Exidor's cult was it had no actual followers. Exidor believed his cult actually had a large following but all the members were invisible.

Exidor believed a Venusian space ship was to come on Labor Day to take the faithful to Venus and destroy the rest of the earth. Exidor maintained a waiting list in his flop house room. He was the only tangible passenger on the list. Exidor's invisible donkey and regular traveling companion was also another passenger. At some point before the spaceship would take them to Venus Exidor believed he was destined to rule the world as a rock star. To that end he would take regular music lesson's at Mindy's father's music store.

Mork eventually confessed to Exidor that he himself is a space alien. Exidor determined Mork was crazy.

The Exidor character appeared in altered form in the underground comic Cerebus. The hermit magician character Necross was strongly based on Exidor. A YuGiOh card called Exodia Necross might itself be a nod to both. Hrm.

As noted above, the character's name was likely a reference to the Exeter character in This Island Earth. This Island Earth was, of course, the movie used for the Mystery Science Theater 3000 movie. The actor who played Mork & Mindy's Exidor himself appeared in a movie parodied on the TV version of MST3K. Donner appeared in Episode #204 "Catalina Caper".